The ternary complex with human IL-2 was formed on EL/Tac 3 cells expressing human L and murine H chains, although human IL-2 was unable to bind to the parental EL-4 cell, which does not express human L chain.

IL-4-mediated inhibition of IL-2-induced IL-2R expression does not seem to be due to the direct interaction between IL-4 and cell surface receptors, inasmuch as preincubation of cells with IL-4 for 60 min at 37 degrees C did not alter the binding of 125I-IL-2 to cells previously cultured for 3 days with SAC plus IL-2.

In this macromolecular complex, the presence of an equilibrium between several conformations has been observed and small molecules have been determined that prevent the interaction between IL-2 and its receptor IL-2R?

However, increased IL-2 secretion in the presence of EC can not fully account for endothelial-induced CD40 ligand up-regulation as (1) the effect of exogenous IL-2 is greater at 24 h than at 6 h, whereas the opposite is true for EC; (2) the effect of saturating levels of IL-2 is considerably smaller than that of EC; and (3) blocking of IL-2 receptors does not fully inhibit endothelial effects on CD40 ligand expression.

We assessed the roles of the various receptor complexes in these responses to IL-2 using antibodies that block the interaction of IL-2 with the intermediate-affinity IL-2R (humanized Mik beta 1) and high- and low-affinity interactions (HTac).

Whereas 2.5% of cell-surface IL-2R expressed 2 days after antigenic stimulation of 2B11 cells were of high affinity for IL-2 (KD = 25 pM), no (less than 0.07%) high affinity binding sites could be detected on the purified soluble IL-2R.

Interleukin-2 (IL-2) which has nocross-resistance with chemotherapy, has given responses in tumors resistant to chemotherapy, and shown to be more effective when tumor burden is low. 13-cis retinoic acid (RA) has immunomodulatory properties, potentially synergistic with IL-2.

Substitution of Asp20 or deletion of Phe124 resulted in inactive analog proteins that were unable to interact with the high-affinity p55/p70 complex or the intermediate-affinity p70 subunit of the interleukin 2 receptor.

We find an entropically favorable high affinity interaction between IL-2 and its alpha receptor, a moderately entropically favorable low affinity interaction between IL-2 and its beta receptor, and no interaction between IL-2 and the shared receptor, gamma(c).

It was found that subclones of the hybridoma that no longer secreted interleukin 2 in response to Ag/H-2, even though they continued to secrete interleukin 2 in response to concanavalin A, also no longer bound specifically to Ag-pulsed monolayers of the appropriate H-2 type.

This result, and similar results in cyclosporin A-treated cells, imply that individual IL-2 transcription factors cannot stably bind their target sequences in vivo without coengagement of all other distinct factors at neighboring sites.

Apoptosis of natural killer (NK) cells can be induced by non-specific physical damage (UV irradiation, heat shock) or by simultaneous ligation of the CD16 and the interleukin-2 receptor (IL-2R) molecules, but not with either anti-CD16 or IL-2 alone.

We demonstrated that IL-2 F42A, an analog that fails to bind to the isolated IL-2R alpha subunit and would be predicted by the hierarchical affinity-conversion model to have impaired binding to cells expressing both chains, instead readily binds to the IL-2R alpha/beta heterodimer in COS cells.

However, ED515-I and 3T3-alpha beta 11, which expressed the IL-2R beta chain, did notbindIL-2 at all when IL-2 binding to their IL-2R alpha chain was blocked with anti-Tac monoclonal antibody, whereas the intermediate affinity binding in ED515-D, Kit225, and Hut102 cells remained.

The gamma chain was detected in lymphoid transfectants of IL-2R beta cDNA, which showed the intermediate-affinity IL-2R, but not in nonlymphoid transfectants of IL-2R beta cDNA, which showed noIL-2 binding activity.

Our data show that this assay is notcrossreactive with hIL-1 beta, hIL-2, hIL-3, hIL-4, hIL-5, hIL-6, hIL-9, hIL-12, hGM-CSF and hTNF-alpha and that it can be completely blocked by an antibody against human IL-10.